Thyroid Disease
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Thyroid Disease
- 1. Thyroid Cancer May 10, 2006
- 12. 45 year old female presents to your office with a thyroid nodule. What questions will you ask her?
- 49. Surgical Anatomy: Vasculature and nerves
- 51. Surgical Anatomy: Anatomical variations of the Right RLN
- 55. Surgical Anatomy: The Parathyroids
Editor's Notes
- Microcarcinoma (<1cm) Histologic variants which show more aggressive behavior and poorer prognosis
- DX: which is why FNA cannot make the diagnosis of malignancy
- Once thought to be a subset of follicular carcinoma, although now seen as its own entity based upon having its own oncogenic expression. More aggressive, evidenced by high….
- Perhaps rare because thyroid cancers are being diagnosed earlier. Sometimes can be challenging to differentiate anaplastic ca from lymphoma, and on occasion will require open bx Patients generally die from airway compromise There was a small study at MGH involving ~60 pts who underwent extensive surgery and there was improved short-term survival compared with those without surgery. Surgery however is very extensive and may involve reconstructing the trachea, etc.
- Sporadic MTC >20% somatic RET mutation
- MENIIA: diagnosed 1 st – 3 rd decade, generally multifocal and bilateral MENIIB: far more aggressive, diagnosed in 1 st decade, multifocal and bilateral. Once manifests clinically, rarely curable. Familial: diagnosed in 5 th – 6 th decade, not as aggressive as MEN syndromes
- Risk compared with general population FNA can sometimes be difficult to determine lymphoma from anaplastic ca, although new immunocytochemistry staining has helped No role for surgery
- Sent by her PCP
- Nodule: is it hard per patient, has she noticed a rapid increase in size? Any other lumps in her neck to suggest LAD? Symptoms: Most patients with cancer are asxs. Uncommonly patients will complain of hoarseness, dysphagia, dyspnea, coughing. Also ask whether patient has had any recent viral illnesses. FHx: Radiation exposure: Likely to be head and neck these days or total body for BMT. In the past, radiotherapy was used for tonsillar, thymic, and adenoid enlargement and acne in children
- Now what?
- Nodules 0.5 – 1cm can generally be palpated. Nodules larger than 4cm are worrisome. Firm nodules more worrisome than soft. (Diffuse irregular firm thyroid gland may indicate thyroiditis.
- Now what?
- Hot nodule may decrease the suspicion of malignancy Detecting metastases and therefore surveillance
- Ultrasound can detect solid nodules 3-4mm and cystic nodules greater than 2mm. Uncommon to have purely cystic nodules, many are mixed. Purely solid nodules carry a higher risk of malignancy.
- Halo sign is usually seen with benign lesions Calcifications Psammoma bodies histologically seen in papillary cancer Because findings on ultrasound are not specific for cancer, FNA typically done at the same time.
- Typically done in conjunction with ultrasound
- Surgical options……
- Contralateral nodules – high rate of multicentric disease Age – recurrence rates are higher in this age group
- In that case…. Controversy here is that as mentioned previously, many of these cancers tend to be multicentric and therefore many proponents of near-total or total thryoidectomy. However, now with radioiodine ablation therapy there are more advocates of lobectomy with isthmusectomy to decrease risk to patient of injury to RLN and parathyroids.
- These are the nodes most commonly involved in differentiated thyroid cancer 80% of the time metastasis occurs to this group of LN Some agrue that while positive LN occur in 20-30% of patients the clinical significance is unclear.
- Level VI: called the central component or paraglandular space includes the prelaryngeal, pretracheal, and paratracheal LN in the tracheoesophageal groove, as well as the anterior superior mediastinal LN. Generally defined as extending from hyoid bone superiorly, innominate vein inferiorly, and carotid sheaths laterally. More extensive dissections are generally only called for with either known metastatic disease and in the case of medullary carcinoma
- AMES scoring system stems from a study done in the late 1970, AGES originated from Mayo Clinic. The AGES system describes a scoring system for presence or absence of these factors. A score of less than 4 is associated with a 20-year mortality rate of less than 1%. The more advanced stages have 5-year survival rates approaching 50%.
- Levothyroxine: differentiated thyroid cancer express the thyrotropin receptor and responds to TSH stimulation by increasing the rate of cell growth – used to decrease risk of recurrence
- Lobectomy, knowing that they may need to have a completion thyroidectomy if tumor > 2cm and widely invasive pathology
- Need to have adequate sample to demonstrate vascular or capsular invasion. Negative frozen section will not change your management.
- Radioiodine ablation is not usually very effective for Hurthle cell, although may still recommend it.
- Goal is to destroy residual thyroid tissue in an effort to decrease the risk of recurrent locoregional disease and to facilitate long-term surveillance with whole body iodine scans. Only studies available at this date are retrospective. According to these studies, benefit is only conferred to those patients with larger tumors (>1.5cm) or with residual disease after surgery. There is no clear benefit for low-risk patients.
- T4a – includes invasion of subc tissue, trachea, esophagus and RLN T4b – invades prevertebral fascia or encases carotid or mediastinal vessels Level VI (pretracheal, paratracheal, prelaryngeal)
- Thyroglobulin glycoprotein produced by normal thyroid tissue and after total thyroidectomy and radioiodine ablation therapy should be undetectable. Checked every 6-12 months for the first 1-2 years Endocrinologist is managing most of this
- Locoregional disease: if surgery not feasible or not complete then proceed with radioiodine therapy, if this is unsuccessful then external beam radiation
- Hypertension issues
- Thought here being that in order to remove all thyroid tissue, it is best to remove the glands and then reimplant them. In patients with MEN2A, implantation should be done in the forearm, as easier access.
- MTC cells do not take up radioiodine. Unfortunately XRT and chemo have not proved all that successful and long-term survival depends on complete surgical removal of the thyroid tissue
- Thyroid gland extends from the cricoid cartilage covering the anterior tracheal rings wrapping around the anterolateral portion of the trachea. Consists of right and left lobes connected by the isthmus which usually extends anterior to the 2 nd and 3 rd tracheal rings. Not uncommonly, a pyramidal lobe is present extending superiorly to the hyoid bone from the isthmus. If fibrous band connection between the hyoid and pyramidal lobe it is termed the “levator of the thyroid gland” Posterior medial aspects of the thyroid lobes are attached to the cricoid cartilage by the ligament of Berry (aka suspensory ligament of the thyroid). Vascular anatomy: Although the thyroid accounts for only 0.4% of our body weight, it accounts for 2% of the total blood flow. It is estimated that during disease states, the flow through the gland can increase 100-fold. Superior thyroid artery (1 st branch off the external carotid) bifurcates into a dominant anterior and smaller posterior branch at the upper lobes. The external branch of the superior laryngeal nerve is often closely associated with the superior thyroid artery at the upper lobe and at risk for injury during dissection. Want to ligate the individual branches of this artery because ligating the main trunk risks injury to the nerve. The inferior thyroid artery emanates from the thyrocervical trunk and passes behind the carotid sheath. It is intimately associated with the RLN. Cannot neglect to mention the thyroid ima artery which is occasionally present and stems from the aorta or the innominate, entering the inferior aspect of the isthmus. Venous drainage: superior, middle, and inferior thryoid veins
- The relationship between the external branch of the superior laryngeal nerve (black) and the superior thyroid artery. The nerve can course inferiorly and medially and may run partly along with or around the artery or the branches of the artery as they enter the superior lobe of the thyroid
- Inability to tense the vocal cord, thereby unable to attain high-pitched notes or project one’s voice (professional speakers/singers)
- This demonstrates the possible anatomic variations of the RLN. Fig A occurs in about 1% of the population. RLN is arising from the vagus at the level of the cricoid and directly enters the larynx. It can be mistaken for an arterial branch. (Left non-recurrent nerve very rare and usually associated with major arterial abnormalities.) Fig B the normal course of the RLN. Running posterior to the CCA then along the tracheoesophageal groove. It can pass behind, in front of, or between the branches of the ITA. It can also have a variant course with regard to the ligament of berry. Fig. C – Rare nonrecurrent nerve and recurrent laryngeal nerve join to form common distal nerve
- The cord is immobilized in the paramedian position Many advocate monitoring the RLN intra-operatively. However this requires that the patient is not paralyzed.
- Particularly at risk during thyroid surgery because of end artery blood supply. If this terminal branch of the ITA is damaged, it results in ischemic necrosis of the gland.